1. Technical Field
The invention relates to flanged covers. More particularly, it relates to flanged valve covers for internal combustion engines having a retainer spring for distributing a closing force applied to the lateral attachment flange.
2. Related Art
Flanged covers are used in a wide variety of applications, particularly where the flange is used to provide a clamping force for sealing the cover to a base. Such covers include valve covers, which are conventionally made of a light weight mild steel sheet material, and together with a seals or gaskets serve to provide sealed enclosures, for the valve lifters, rocker arms and valves in the cylinder heads of internal combustion engines. Depending upon the type of engine there may be a single valve cover bolted to the engine head as in the case of an in-line engine or several valve covers in the case of a V-6, V-8, V-12 engines, each enclosing a bank of valves. Normally, a gasket or seal is disposed between the valve cover and the head to which it is bolted to prevent oil leakage. Valve covers have conventionally been formed from mild steel, but may also be molded from a variety of engineering plastics, including engineering thermoplastic or thermoset materials, in order to facilitate weight reduction, or the formation of covers having complex geometries, or combinations of the above.
Depending on the material used to form the valve cover and its thickness, particularly the thickness of the sealing flange, the cover, flange or both may, over a period of time, tend to warp and pull away somewhat from the head producing uneven clamping pressure on the gasket, which may in turn result in oil leaks. This warping can be caused by several conditions, including the uneven tightening or torquing of the bolts which secure the valve cover to the head, or by engine overheating, or due to creep or other deformation phenomena associated with the material selected for use in the valve cover. This problem can be exacerbated in plastic valve covers where creep and other deformation phenomena can be more pronounced, particularly at engine operating temperatures and in the regions which lie between or mediate the fasteners used to attach the valve cover, such as threaded bolts which are tightened into the cylinder head.
Therefore, improved cover assemblies, such as valve cover assemblies, are desired which provide improved clamping and closure characteristics and which reduce fluid leakage, such as oil leakage.